Shelducks are a group of large ducks belonging to the genus Tadorna. There are around 10 species found across Eurasia, Africa, Australia and New Zealand. In South Africa, there are two species of shelduck that reside or migrate through the country: the South African Shelduck (Tadorna cana) and the Ruddy Shelduck (Tadorna ferruginea).
Shelducks are known for their large size compared to many other duck species. Their exact dimensions can vary based on sex, age and geographic location. In this article, we will look at the typical body measurements of South African Shelducks and Ruddy Shelducks found in South Africa. Understanding the size of these birds can help us appreciate their place in local wetland ecosystems.
South African Shelduck Size
The South African Shelduck is endemic to southern Africa. It is a large, goose-like duck with a dark chestnut body, white wings, a greenish-black head and a red bill. Males and females look similar, but the females are slightly smaller.
Some key body measurements for South African Shelducks are:
Length
– Total length: 66–81 cm (26–32 in)
– Wingspan: 110–138 cm (43–54 in)
Mass
– Males: 1.3–2.4 kg (2.9–5.3 lb)
– Females: 1.1–1.8 kg (2.4–4.0 lb)
So males are around 15-20% heavier than females on average.
Wings
– Wing chord length: 38–42.5 cm (15.0–16.7 in)
The wingspan is around 1.5 times the total length, giving the South African Shelduck powerful flight for their large size.
Ruddy Shelduck Size
The Ruddy Shelduck has a wide distribution across Africa, Asia and Europe. In South Africa, it is mainly a winter migrant arriving between April and September.
The Ruddy Shelduck is slightly smaller than the South African Shelduck. Some key measurements are:
Length
– Total length: 58–74 cm (23–29 in)
– Wingspan: 110–127 cm (43–50 in)
Mass
– Males: 1.1–1.9 kg (2.4–4.2 lb)
– Females: 0.9–1.5 kg (2.0–3.3 lb)
Again, the males are around 15% heavier than females on average.
Wings
– Wing chord length: 32.5–38.5 cm (12.8–15.2 in)
Size Comparisons
To summarize the size differences:
South African Shelduck
– Length: 66–81 cm
– Wingspan: 110–138 cm
– Mass:
– Males: 1.3–2.4 kg
– Females: 1.1–1.8 kg
Ruddy Shelduck
– Length: 58–74 cm
– Wingspan: 110–127 cm
– Mass:
– Males: 1.1–1.9 kg
– Females: 0.9–1.5 kg
So the South African Shelduck is around 10% longer and heavier than the Ruddy Shelduck. However, their wingspans are similar.
This table summarizes the size differences:
| Species | Length (cm) | Wingspan (cm) | Mass – Males (kg) | Mass – Females (kg) |
|---|---|---|---|---|
| South African Shelduck | 66-81 | 110-138 | 1.3-2.4 | 1.1-1.8 |
| Ruddy Shelduck | 58-74 | 110-127 | 1.1-1.9 | 0.9-1.5 |
Why the Size Difference?
A few key factors likely contribute to the South African Shelduck being moderately larger than the Ruddy Shelduck:
– The South African Shelduck resides year-round in South Africa, whereas the Ruddy Shelduck migrates from further north. Larger body size may help the South African Shelduck retain heat better through cold winters.
– As an endemic species, the South African Shelduck is highly adapted to local habitat conditions in South Africa. Its large size may give it advantages in competing for resources and establishing breeding territories.
– The Ruddy Shelduck has a much wider distribution across Africa, Europe and Asia. Smaller body size may enable it to migrate longer distances more efficiently.
– Male shelducks are larger than females, which is common in many duck species and other birds. The larger size of males may have evolved for gaining access to females for breeding.
Habitats and Diet
Understanding where shelducks live and what they eat can also provide clues into their size and adaptations:
Habitats
– South African Shelducks inhabit a variety of wetlands, including tidal mudflats, estuaries, lakes, dams and ponds.
– Ruddy Shelducks use similar habitats during their wintering in South Africa, as well as offshore marine waters.
– Their large size helps shelducks walk and forage in shallow water better than smaller ducks. Long powerful bills let them feed on molluscs, aquatic insects and vegetation.
Diet
– South African Shelducks feed mainly on plant material, molluscs, insects, worms, fish and amphibians.
– Ruddy Shelducks have a similar diet, but include more plant material from grazing grasslands and agricultural fields.
– The varied diet and foraging activities of shelducks requires a large muscular body and substantial energy reserves – hence their relatively large size.
Conservation Status
Due to several threats, both species of shelducks have declining populations:
– The South African Shelduck is classified as Near Threatened with decreasing numbers. Total population is uncertain but likely less than 10,000 mature individuals.
– The Ruddy Shelduck is classified as Least Concern but has possibly undergone moderate declines in the past 30 years.
Major threats include:
– Habitat loss and degradation – draining wetlands for development
– Disturbance from human activities
– Pollution
– Unsustainable harvesting of eggs and adults
More habitat conservation and protections for shelducks are needed to ensure stable future populations. Their specialized niches as large ducks may be disrupted if declines continue.
Conclusion
– The South African Shelduck and Ruddy Shelduck are the two largest duck species found in South Africa.
– South African Shelducks are moderately larger, with males reaching around 2.4 kg compared to 1.9 kg for Ruddy Shelduck males.
– Their large size aids them in foraging and establishing breeding territories in wetland habitats.
– Both shelduck species are in decline and need additional protections to preserve their unique roles as South Africa’s giant ducks.
– Continued research on the ecosystems, diet and breeding biology of shelducks is important to support conservation efforts. Monitoring their body condition and sizes over time can indicate population health and adaptions to changing conditions.
– Wetland protection and management will benefit shelducks and maintain their stature as the biggest ducks around. With supportive policies, these magnificent waterfowl can grace South Africa’s lakes, estuaries and coastlines for generations to come.
